rng-tools: uci-fy, default to doing nothing

Enabling the default configuration will pipe /dev/urandom back into
/dev/random ala the current package behavior.  Because this amounts to
disabling the in-kernel entropy estimation, default disabled.

While here, uci-paramaterize the high watermark.
While here, add a pre-command hook for real RNGs that need 'stty raw'
or other such hooks.  (e.g. the TrueRNG devices)

As offered in github openwrt/packages#3422, take over maintainership.

See github openwrt/packages#3142.

Signed-off-by: Nathaniel Wesley Filardo <nwfilardo@gmail.com>

utils/rng-tools/files/rngd.init

@@ -3,12 +3,20 @@
 
 START=98
 
-RNGD_AMOUNT=4000
-RNGD_DEVICE="/dev/urandom"
-# Use /dev/urandom as source, as hardware sources like /dev/hwrng are usually not present
+RNGD_FILLWATER=$(uci -q get system.@rngd[0].fill_watermark)
+RNGD_DEVICE=$(uci -q get system.@rngd[0].device)
+RNGD_ENABLED=$(uci -q get system.@rngd[0].enabled)
+RNGD_PRECMD=$(uci -q get system.@rngd[0].precmd)
+
+: ${RNGD_FILLWATER:=4000}
+
+echo PRECMD=\'$RNGD_PRECMD\'
 
 start() {
-	service_start /sbin/rngd -r $RNGD_DEVICE -W $RNGD_AMOUNT
+    [ 1 -eq "$RNGD_ENABLED" ] && {
+      [ -z "${RNGD_PRECMD}" ] || ${RNGD_PRECMD} ${RNGD_DEVICE}
+      service_start /sbin/rngd -r ${RNGD_DEVICE} -W ${RNGD_FILLWATER}
+    }
 }
 
 stop() {

utils/rng-tools/files/rngd.uci_defaults

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+uci -q show system.@rngd[0] || {
+	uci add system rngd
+	uci set system.@rngd[0].enabled=0
+	uci set system.@rngd[0].device=/dev/urandom
+	uci commit
+}